Adhesive film

ABSTRACT

The adhesive film includes a film-like adhesive layer, a light release separator and a heavy release separator that are laminated on either side of the adhesive layer, and a carrier film further laminated on the heavy release separator. The outer edges of the light release separator and the carrier film forming the outer layer extend outward beyond the outer edge of the adhesive layer and the heavy release separator forming the inner layer. The outer edge sections of the adhesive layer are thereby protected. The outer edge section of the carrier film is gripped and released first, after which the outer edge section of the light release separator is gripped and released, and finally the heavy release separator is released, thereby allowing each separator and the carrier film to be reliably and easily released in the prescribed order.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an adhesive film.

2. Related Background Art

In recent years, touch panels are being incorporated in the liquidcrystal display devices of cellular phones, portable gaming devices,digital cameras, car navigation systems, handheld computers, portabledata terminals (PDA) and the like. Such liquid crystal display devices(hereunder also referred to as “touch panel displays”) are constructedin a layered manner, with a protective panel, touch panel and liquidcrystal panel in that order, there being disposed transparent adhesivefilms between the protective panel and touch panel and between the touchpanel and liquid crystal panel (see PTL 1, for example). Because suchadhesive films help increase the brightness and visibility of thedisplay while also functioning as a shock absorption material, they areindispensable components of the display structure.

[PTL 1] Japanese Unexamined Patent Application Publication No.2008-83491

SUMMARY OF THE INVENTION

The adhesive films mentioned above are generally handled in athree-layer structure form, with both sides of the adhesive layersandwiched between releasable base material layers. An adhesive film ofthis type is produced by coating a liquid adhesive composition onto oneof the base material layers, irradiating it with active light rays suchas ultraviolet rays if necessary to induce semi-curing or curing andform an adhesive layer, and then layering the other base material layeron the adhesive layer. The adhesive layer is preferably formedbeforehand to the size of the liquid crystal display device in which itis intended to be used. However, it is difficult to coat adhesive layersto prescribed sizes. It is therefore effective to use a blade or othertool to cut out the adhesive layer formed on the base material layerduring the process of producing the adhesive film, so that the adhesivelayer can be obtained in the desired shape. Yet, adhesive films formedin such a manner are considered to be responsible for releasabilityproblems of base material layers from the adhesive layer. An example ofthe releasability problems is such that the adhesive layer is pulledtoward the first base material layer during release of the first basematerial layer from the adhesive layer, causing it to be peeled from theother base material layer. This problem can be occur even in case where,the design is such that, in order to allow release of first one basematerial layer and then the other base material layer, the peel strengthbetween the first base material layer and the adhesive layer is made tobe lower than the peel strength between the other base material layerand the adhesive layer.

Being the result of much effort toward finding a solution to thisproblem, the invention provides an adhesive film that protects theadhesive layer while facilitating reliable release of each base materiallayer in order, without releasability problems.

The adhesive film of the invention comprises a film-like adhesive layer,first and second base material layers laminated in a manner sandwichingthe adhesive layer, and a carrier layer further laminated on the secondbase material layer, wherein the outer edges of the first base materiallayer and the carrier layer constituting the outer layer extend outwardbeyond the outer edges of the adhesive layer and the second basematerial layer constituting the inner layer.

In this type of adhesive film, the outer edges of the first basematerial layer and carrier layer, which constitute the outer layer,extend outward beyond the outer edges of the adhesive layer and thesecond base material layer, which constitute the inner layer. Thisreliably protects the outer edges of the adhesive layer during storageand transport of the adhesive film. When the adhesive layer is to beattached to an adherend, the outer edge section of the carrier layerthat is extended outward may be gripped for easy release of the carrierlayer. The outer edge section of the first base material layer may thenbe gripped for easy release of the first base material layer. Since thesecond base material layer thus remains on one side of the adhesivelayer, protection of the adhesive layer is maintained by the second basematerial layer when one side of the adhesive layer is to be attached toan adherend. The second base material layer may then be subsequentlyreleased and the other side of the adhesive layer attached to adifferent adherend so that the adhesive layer is disposed between thepair of adherends.

The outer edge of the second base material layer is preferably flushwith the outer edge of the adhesive layer. Since this will accentuatethe difference in releasability between the first base material layerand the second base material layer, it will be possible to more easilyrelease the first base material layer before releasing the second basematerial layer. Furthermore, if the outer edge of the second basematerial layer is aligned with the outer edge of the adhesive layer, theouter edge of the adhesive layer will become more distinct, thusfacilitating positioning of the adhesive layer with the adherend.

The outer edge of the carrier layer preferably extends outward beyondthe outer edge of the first base material layer. This will furtherfacilitate gripping of the outer edge sections of the carrier layer,allowing the carrier layer to be more easily released.

The peel strength between the first base material layer and the adhesivelayer is also preferably lower than the peel strength between the secondbase material layer and the adhesive layer. This will accentuate thedifference in releasability between the first base material layer andthe second base material layer, thus making it be possible to moreeasily release the first base material layer before releasing the secondbase material layer.

In addition, the peel strength between the second base material layerand the carrier layer is preferably lower than the peel strength betweenthe second base material layer and the adhesive layer. This willaccentuate the difference in releasability between the carrier layer andthe second base material layer, thus making the carrier layer moreeasily releasable.

The adhesive film of the invention can protect the adhesive layer whilefacilitating reliable release of each base material layer in order,without releasability problems.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an embodiment of an adhesive film according tothe invention.

FIG. 2 is a perspective view of an embodiment of an adhesive filmaccording to the invention.

FIG. 3 is a side view of another embodiment of an adhesive filmaccording to the invention.

FIG. 4 is a cross-sectional view of a preliminary film.

FIG. 5 is a cross-sectional diagram illustrating a cutting step.

FIG. 6 is a cross-sectional diagram illustrating a removal step.

FIG. 7 is a cross-sectional diagram illustrating a removal step.

FIG. 8 is a cross-sectional diagram illustrating a removal step.

FIG. 9 is a cross-sectional diagram illustrating an attachment step.

FIG. 10 is a cross-sectional diagram illustrating a carrier filmreleasing step.

FIG. 11 is a cross-sectional diagram illustrating a light releaseseparator-releasing step.

FIG. 12 is a cross-sectional diagram illustrating a step of attachmentfor a side of an adhesive layer onto an adherend.

FIG. 13 is a cross-sectional diagram illustrating a heavy releaseseparator-releasing step.

FIG. 14 is a cross-sectional diagram illustrating a step of attachmentfor a side of an adhesive layer onto an adherend.

FIG. 15 is a schematic diagram illustrating a method of setting a sampleon a macrodynamic viscoelasticity meter.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIGS. 1 and 2, the adhesive film 1 of the inventioncomprises a transparent film-like adhesive layer 2, a light releaseseparator 3 (first base material layer) and a heavy release separator 4(second base material layer) that are laminated on either side of theadhesive layer 2, and a carrier film 5 (carrier layer) further laminatedon the heavy release separator 4. For assembly of a touch panel displayfor a portable terminal, for example, the adhesive film 1 serves toprovide an adhesive layer 2 between a protective panel and a touchpanel, and between the touch panel and a liquid crystal panel.

The adhesive layer 2 is formed, for example, by an adhesive compositionthat includes (A) an acrylic acid-based derivative polymer, (B) anacrylic acid-based derivative and (C) a polymerization initiator. The(A) acrylic acid-based derivative polymer may be obtained bypolymerizing the (B) acrylic acid-based derivative, and preferably itsweight-average molecular weight is between 10,000 and 1,000,000 (asmeasured using a calibration curve for standard polystyrene obtained bygel permeation chromatography). The acrylic acid-based derivativepolymer may be a polymer obtained by polymerization in combination witha monomer other than an acrylic acid-based derivative. Theweight-average molecular weight can be measured using the followingapparatus and measuring conditions.

Apparatus: HCL-8320GPC High-speed GPC (detector: differentialrefractometer or UV) (Tosoh Corp.)

Solvent: Tetrahydrofuran (THF) Column: TSKGEL SuperMultipore HZ-H (TosohCorp.)

Column size: Column length=15 cm, Inner column diameter: 4.6 mmMeasuring temperature: 40° C.Flow rate: 0.35 ml/minSample concentration: 10 mg/5 mL THFInjection rate: 20 μl

The (B) acrylic acid-based derivative may be acrylic acid or methacrylicacid, or any of their derivatives. Specifically, these include(meth)acrylic acid alkyl having C1-20 alkyl, benzyl (meth)acrylate,alkoxyalkyl (meth)acrylates, aminoalkyl (meth)acrylates, (meth)acrylicacid esters of (diethyleneglycol ethyl ether), (meth)acrylic acid estersof polyalkyleneglycol alkyl ethers, (meth)acrylic acid esters ofpolyalkyleneglycol aryl ethers, (meth)acrylic acid esters with alicyclicgroups, fluorinated alkyl acrylates, (meth)acrylic acid esters withhydroxyl groups, such as 2-hydroxyethyl methacrylate, 3-hydroxypropylmethacrylate, 4-hydroxybutyl methacrylate, 2-hydroxyethyl acrylate,3-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, glycerol methacrylateand glycerol acrylate, glycidyl (meth)acrylates, acrylamides,(meth)acryloylmorpholine, and the like, which have one polymerizableunsaturated bond in the molecule. Any of these may be used alone or inmixtures of two or more.

A monomer with 2 or more polymerizable unsaturated bonds in the moleculemay also be used together with the aforementioned monomers that have onepolymerizable unsaturated bond in the molecule. Such monomers includebisphenol A di(meth)acrylate, 1,4-butanediol di(meth)acrylate,1,3-butyleneglycol di(meth)acrylate, diethyleneglycol di(meth)acrylate,glycerol di(meth)acrylate, neopentyl glycol di(meth)acrylate,polyethyleneglycol di(meth)acrylate, polypropyleneglycoldi(meth)acrylate, tetraethyleneglycol dimethacrylate, trimethylolpropanetrimethacrylate, pentaerythritol tri(meth)acrylate,tris((meth)acryloxyethyl)isocyanurate, pentaerythritoltetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate,dipentaerythritol hexa(meth)acrylate, dipentaerythritolpenta(meth)acrylate, and di(meth)acrylates with urethane bonds. Thesemonomers may also be used alone or in combinations of two or more. Fromthe viewpoint of shapeability of the adhesive layer 2, it is preferredto use a monomer with 2 or more polymerizable unsaturated bonds in themolecule in component (B).

The term “(meth)acrylate” refers to the “acrylate” and its corresponding“methacrylate”. Similarly, the term “(meth)acrylic” refers to the“acrylic” and its corresponding “methacrylic” compound, and“(meth)acryloyl” refers to the “acryloyl” and its corresponding“methacryloyl” compound.

The (C) polymerization initiator may employ a photopolymerizationinitiator, which may be selected from among known materials such asketone-based, acetophenone-based, benzophenone-based,anthraquinone-based, benzoin-based, acylphosphine oxide-based, sulfoniumsalt, diazonium salt and onium salt compounds. Particularly preferredare ketone-based compounds such as 1-hydroxycyclohexylphenyl ketone, andacylphosphine oxide-based compounds such asbis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide,bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide and2,4,6-trimethylbenzoyl-diphenylphosphine oxide, from the viewpoint oftransparency and curing properties.

The content of component (A) is preferably 15-80 wt %, more preferably15-60 wt % and even more preferably 15-50 wt % with respect to the totalweight of the adhesive composition. The content of component (B) ispreferably 15-80 wt %, more preferably 30-80 wt % and even morepreferably 40-80 wt % with respect to the total weight of the adhesivecomposition. If the contents of component (A) and component (B) arewithin these ranges, the viscosity of the adhesive composition will bewithin the proper viscosity range for formation of the adhesive layer,and the moldability will be satisfactory. The adhesion and transparencyof the adhesive layer 2 will also be improved. The content of component(C) is preferably 0.05-5 wt %, more preferably 0.1-3 wt % and even morepreferably 0.1-0.5 wt % with respect to the total weight of the adhesivecomposition. By limiting the content of component (C) to no greater than5 wt % it is possible to increase the light transmittance of theadhesive composition and avoid its yellowing, to obtain a superioradhesive layer 2.

The adhesive layer 2 is obtained by, for example, coating a liquidadhesive composition comprising components (A) to (C) on a heavy releaseseparator 4 to a desired film thickness, irradiating it with an activeenergy beam for curing, and then shaping it by cutting to the desiredsize. From the viewpoint of adhesion, the adhesive layer 2 is preferablycomposed mainly of a structural unit derived from a (meth)acrylic acidalkyl having C4-18 alkyl. Here, “composed mainly of” refers to the mostabundant component constituting the adhesive layer 2. The coatedadhesive composition may be irradiated with active light rays such asultraviolet rays. The thickness of the adhesive layer 2 is preferablybetween 0.1 mm and 1 mm, and more preferably between 0.15 mm (150 μm)and 0.5 mm (500 μm). With this range of thickness, the adhesive layer 2will be able to exhibit an even more superior effect when applied in adisplay.

The storage elastic modulus of the adhesive layer 2 at 25° C. ispreferably between 1.0×10³ Pa and 1.0×10⁶ Pa, and more preferablybetween 1.0×10⁴ Pa and 5.0×10⁵ Pa.

The storage elastic modulus may be measured as follows. First, twoadhesive layers 2 with thicknesses of 250 μm are stacked for a thicknessof approximately 500 μm, and the stack is cut into a 10 mm square toform a sample S. Two samples S are prepared and set on a macrodynamicviscoelasticity meter by means of a jig 100. As shown in FIG. 15, thejig 100 comprises a pair of mounting jigs 100A, 100B that are mounted onthe macrodynamic viscoelasticity meter so as to face each other. Themounting jig 100A is provided with a plate P1 that extends toward themounting jig 100B. The mounting jig 100B is provided with a pair ofplates P2, P2 each facing a side of the plate P1, and extending towardthe mounting jig 100A. Each plate P2 is attached to the plate P1 througha sample S. The mounting jigs 100A, 100B are thus moved away from eachother by the macrodynamic viscoelasticity meter, and the storage elasticmodulus is measured. The macrodynamic viscoelasticity meter used was aSolids Analyzer RSA-II by Rheometric Scientific, and the measuringconditions were shear sandwich mode, 1.0 Hz frequency, with temperatureincrease at 5° C./min in a measuring temperature range of −20° C. to100° C.

The peel strength of the adhesive layer 2 for a glass plate ispreferably between 5 N/10 mm and 20 N/10 mm, and more preferably between7 N/10 mm and 15 N/10 mm. The thickness of the adhesive layer 2 ispreferably between 100 μm and 500 μm and more preferably between 150 μmand 400 μm. The planar shape of the adhesive layer 2 may beappropriately designed depending on the adherend to which it will beapplied, and for example, the effect of the invention will beprominently exhibited with a rectangular shape having long sides between50 mm and 500 mm and short sides between 30 mm and 400 mm, and even moreprominently exhibited with a rectangular shape having long sides between100 mm and 300 mm and short sides between 80 mm and 280 mm. The lighttransmittance of the adhesive layer 2 is preferably at least 80%, morepreferably at least 90% and most preferably at least 95% with respect tolight rays in the visible light range (wavelength: 380-780 nm). Thelight transmittance may be measured using a spectrophotometer. As anexample, the spectrophotometer may be a Hitachi Model U-3310spectrophotometer (with integrating sphere). The light transmittance ofthe adhesive layer 2 can be calculated by using a spectrophotometer tomeasure the light transmittance of an adhesive layer-attached glassplate, comprising a 500 μm-thick glass plate and the adhesive layer 2adjusted to a thickness of 175 μm, and subtracting the lighttransmittance of the glass plate from the light transmittance of theadhesive layer-attached glass plate.

The light release separator 3 may be a polymer film such as polyethyleneterephthalate, polypropylene, polyethylene or polyester, and ispreferably a polyethylene terephthalate film (PET film). The thicknessof the light release separator 3 is preferably between 25 μm and 125 μm,more preferably between 30 μm and 100 μm and most preferably between 40μm and 75 μm.

The heavy release separator 4 may also be a polymer film such aspolyethylene terephthalate, polypropylene, polyethylene or polyester,and is preferably a polyethylene terephthalate film (PET film). Thethickness of the heavy release separator 4 is preferably between 50 μmand 150 μm, more preferably between 60 μm and 125 μm and most preferablybetween 70 μm and 100 μm.

The carrier film 5 may likewise be a polymer film such as polyethyleneterephthalate, polypropylene, polyethylene or polyester, and ispreferably a polyethylene terephthalate film (PET film). The thicknessof the carrier film 5 is preferably between 15 μm and 100 μm, morepreferably between 20 μm and 80 μm and most preferably between 20 μm and50 μm.

The outer edge 4 a of the heavy release separator 4 is essentially flushwith the outer edge 2 a of the adhesive layer 2. The outer edges 3 a, 5a of the light release separator 3 and the carrier film 5 extend outwardbeyond the outer edge 2 a of the adhesive layer 2. The outer edge 5 apreferably extends outward even beyond the outer edge 3 a.

The amount by which the outer edge 3 a extends outward beyond the outeredge 2 a is preferably between 2 mm and 15 mm and more preferablybetween 4 mm and 10 mm. The amount by which the outer edge 5 a extendsoutward beyond the outer edge 2 a is preferably between 3 mm and 25 mmand more preferably between 5 mm and 20 mm. Preferably, the inequalityQ>P is satisfied, where P is the amount by which the outer edge 3 aextends outward beyond the outer edge 2 a, and Q is the amount by whichthe outer edge 5 a extends outward beyond the outer edge 3 a.

The peel strength between the light release separator 3 and the adhesivelayer 2 is preferably lower than the peel strength between the heavyrelease separator 4 and the adhesive layer 2. The peel strength betweenthe carrier film 5 and the heavy release separator 4 is lower than thepeel strength between the heavy release separator 4 and the adhesivelayer 2. The peel strength between the carrier film 5 and the heavyrelease separator 4 is even more preferably lower than the peel strengthbetween the light release separator 3 and the adhesive layer 2, but theeffect of the invention will not be impaired if it is higher.

The peel strength between the light release separator 3 and the adhesivelayer 2 is preferably 0.01 N/25 mm to 0.4 N/25 mm, the peel strengthbetween the heavy release separator 4 and the adhesive layer 2 ispreferably 0.3 N/25 mm to 1.5 N/25 mm, and the peel strength between thecarrier film 5 and the heavy release separator 4 is preferably 0.005N/25 mm to 0.3 N/25 mm. Also, the inequalities T>S and T>U arepreferably satisfied, where S is the peel strength between the lightrelease separator 3 and the adhesive layer 2, T is the peel strengthbetween the heavy release separator 4 and the adhesive layer 2, and U isthe peel strength between the carrier film 5 and the heavy releaseseparator 4. The relationship between S and U may be either S>U or U>S,but S>U is especially preferred.

The peel strength was measured using a TENSILON RTG-1210 UniversalTester by A&D. The measuring conditions were with 90 degree peeling forthe peel strength between the light release separator 3 and the adhesivelayer 2, the peel strength between the heavy release separator 4 and theadhesive layer 2 and the peel strength between the carrier film 5 andthe heavy release separator 4. The peel strength between the glass plateand the adhesive layer 2 was measured with 180 degree peeling.

Since the outer edges 3 a, 5 a of the light release separator 3 and thecarrier film 5 forming the outer layer thus extend outward beyond theouter edges 2 a, 4 a of the adhesive layer 2 and the heavy releaseseparator 4 forming the inner layer, the outer edge sections of theadhesive layer 2 are reliably protected during storage and transport ofthe adhesive film 1.

The peel strength between the separators 3,4 and the adhesive layer 2may be adjusted by surface treatment of the separators 3,4, for example.Surface treatment of the separators 3,4 can be accomplished by releasetreatment with a silicone-based compound or fluorine-based compound.Also, the peel strength between the carrier film 5 and the heavy releaseseparator 4 may be adjusted by the type and thickness of glue formedbetween the carrier film 5 and the heavy release separator 4. The typeof the glue formed between the carrier film 5 and the heavy releaseseparator 4 may be an acrylic adhesive, for example. The thickness ofthe glue formed between the carrier film 5 and the heavy releaseseparator 4 is preferably 0.1 to 10 μm and more preferably 1 to 5 μm.

When the glue is formed over the entire region of the surface 5 b on theadhesive layer 2 side of the carrier film 5, the glue will be exposed atan outer side of the outer edge 4 a of the heavy release separator 4. Inthis case, it is preferred to provide a film 4A covering the surface 5 bat the outer side of the outer edge 4 a of the heavy release separator4, as shown in FIG. 3. The film 4A may be made of the same material asthe heavy release separator 4, for example. Providing a film 4A willcover the glue over the entire region of the surface 5 b, thuseffectively preventing the exposed glue from becoming attached to othersections, or foreign matter from becoming attached to the exposed glue,so that the usability of the adhesive film 1 can be improved.

The adhesive film 1 described above may be produced in the followingmanner. First, a preliminary film 10 is prepared comprising the heavyrelease separator 4, the adhesive layer 2 and a temporary separator 6laminated on the carrier film 5, as shown in FIG. 4. The temporaryseparator 6 is a layer made of the same material as the light releaseseparator 3, for example.

Next, a die cutter (not shown) equipped with a blade B is used to cutthe temporary separator 6, the adhesive layer 2 and the heavy releaseseparator 4 into the desired shape. The die cutter may be a crank-typedie cutter or a rotary-type die cutter. In this step, the blade B ispassed through the temporary separator 6, the adhesive layer 2 and theheavy release separator 4 to a depth reaching the carrier film 5, asshown in FIG. 5. This forms a notch 5 c on the surface 5 b on theadhesive layer 2 side of the carrier film 5. Since the blade B reachesfrom the temporary separator 6 to the carrier film 5, it is possible tocompletely cut the adhesive layer 2 and heavy release separator 4. Whenit is possible to cut the heavy release separator 4 without forming anotch 5 c, formation of the notch 5 c may be omitted.

Next, the outer sections of the temporary separator 6, adhesive layer 2and heavy release separator 4 are removed, as shown in FIG. 6. As thisis done, the film 4A may be formed by removing only the outer sectionsof the temporary separator 6 and adhesive layer 2, without removing theouter section of the heavy release separator 4 so that it is left on thecarrier film 5, as shown in FIG. 7. Next, the temporary separator 6 isreleased from the adhesive layer 2, as shown in FIG. 8, and the lightrelease separator 3 is attached to the adhesive layer 2, as shown inFIG. 9. This step completes the adhesive film 1.

The adhesive film 1 may be used in the following manner for assembly ofa display. First, the carrier film 5 is released from the heavy releaseseparator 4, as shown in FIG. 10. The outer edge 5 a of the carrier film5 extends outward beyond the outer edges 2 a, 4 a of the adhesive layer2 and the heavy release separator 4, as described above. Thus, the outeredge section of the carrier film 5 that is extended outward may begripped for easy release of the carrier film 5. The outer edge 5 a ofthe carrier film 5 preferably extends outward beyond the outer edge 3 aof the light release separator 3. This will further facilitate grippingof the outer edge sections of the carrier film 5, allowing the carrierfilm 5 to be more easily released. The peel strength between the carrierfilm 5 and the heavy release separator 4 is lower than the peel strengthbetween the heavy release separator 4 and the adhesive layer 2. Thiswill accentuate the difference in releasability between the carrier film5 and the heavy release separator 4, thus making the carrier film 5 morereleasable from the heavy release separator 4.

Next, as shown in FIG. 11, the light release separator 3 is releasedfrom the adhesive layer 2 to expose the adhesive side 2 b of theadhesive layer 2. As mentioned above, the peel strength between thelight release separator 3 and the adhesive layer 2 is lower than thepeel strength between the heavy release separator 4 and the adhesivelayer 2. In a conventional adhesive film, release often cannot beaccomplished as designed even when the peel strengths are different.However, since the outer edge 3 a of the light release separator 3extends outward beyond the outer edges 2 a, 4 a of the adhesive layer 2and the heavy release separator 4, the outer edge 3 a of the lightrelease separator 3 becomes the outwardmost extended edge after thecarrier film 5 has been released. This will render the outer edge 3 a ofthe light release separator 3 more easy to grip than the outer edge 4 aof the heavy release separator 4, so that the light release separator 3will be easier to release than the heavy release separator 4. Therefore,gripping the outer edge section of the light release separator 3 allowsthe light release separator 3 to be easily released before release ofthe heavy release separator 4.

In the adhesive film 1, the outer edge 4 a of the heavy releaseseparator 4 is essentially flush with the outer edge 2 a of the adhesivelayer 2. With this construction, the difference in releasability betweenthe light release separator 3 and the heavy release separator 4 willbecome even more prominent. Therefore, the light release separator 3 canbe easily released before release of the heavy release separator 4.

In addition, since the heavy release separator 4 is protected by thecarrier film 5 up to the immediately previous step, damage to thesurface of the heavy release separator 4 is minimized. This rendersdamage to the adhesive layer 2 highly visible, so that any damage in theadhesive layer 2 can be easily eliminated before attachment to anadherend.

Next, as shown in FIG. 12, the adhesive side 2 b of the adhesive layer 2is attached to the adherend A1 and pressed with a roller R, for example.The adherend A1 may be, for example, a liquid crystal panel, aprotective panel (glass plate, acrylic resin board, polycarbonate boardor the like), or a touch panel. Since the heavy release separator 4remains on the adhesive side 2 c of the adhesive layer 2, protection ofthe adhesive layer 2 is maintained by the heavy release separator 4 whenthe adhesive side 2 b of the adhesive layer 2 is attached to an adherendA1. In addition, since the outer edge 4 a of the heavy release separator4 and the outer edge 2 a of the adhesive layer 2 are aligned, theposition of the outer edge 2 a of the adhesive layer 2 becomes moredefinite and positioning between the adhesive layer 2 and adherend A1 isfacilitated.

Next, as shown in FIG. 13, the heavy release separator 4 is releasedfrom the adhesive layer 2 to expose the adhesive side 2 c of theadhesive layer 2. Then, as shown in FIG. 14, the adhesive side 2 c ofthe adhesive layer 2 is attached to the adherend A2 and heated andpressed. The adherend A2 may be, for example, a liquid crystal panel, aprotective panel or a touch panel. In the steps described above, theadhesive layer 2 is disposed between the adherend A1 and the adherendA2.

Thus, the adhesive film 1 can protect the adhesive layer 2 whilefacilitating reliable release of each separator 3,4 and the carrier film5 in the prescribed order, without releasability problems.

The embodiments described above are preferred embodiments of theinvention, but the invention is not necessarily limited thereto and mayincorporate various modifications within the scope of the gist thereof.

What is claimed is:
 1. A method of making a display, comprising:providing an adhesive film and two adherends, the adhesive filmcomprising: an adhesive layer; first and second base material layerslaminated in a manner sandwiching the adhesive layer; and a carrierlayer further laminated on the second base material layer, the carrierlayer being in direct contact with the second base material layer;wherein the first base material layer and the carrier layer are atopposite sides of the adhesive layer; and wherein the outer edges of thefirst base material layer and the carrier layer extend outward beyondthe outer edges of the adhesive layer and the second base materiallayer; releasing the carrier layer; after releasing the carrier layer,releasing the first base material layer; after releasing the first basematerial layer, attaching the adhesive layer to one adherend of the twoadherends; after attaching the adhesive layer to the one adherend,releasing the second base material layer from the adhesive layer; andthereafter, attaching the adhesive layer to the other adherend of thetwo adherends, such that the adhesive layer is disposed between the twoadherends.
 2. The method according to claim 1, wherein the outer edge ofthe second base material layer is essentially flush with the outer edgeof the adhesive layer.
 3. The method according to claim 1, wherein theouter edge of the carrier layer extends outward beyond the outer edge ofthe first base material layer.
 4. The method according to claim 1,wherein the peel strength between the first base material layer and theadhesive layer is lower than the peel strength between the second basematerial layer and the adhesive layer.
 5. The method according to claim1, wherein the peel strength between the second base material layer andthe carrier layer is lower than the peel strength between the secondbase material layer and the adhesive layer.